Method and apparatus for making uniform and ultrasmall nanoparticles

ABSTRACT

A system comprising: a plasma production chamber configured to produce a plasma; a reaction chamber vaporize a precursor material with the plasma to form a reactive mixture; a quench chamber having a frusto-conical surface and a quench region formed within the quench chamber between an ejection port of the reaction chamber and a cooled mixture outlet, wherein the quench region configured to receive the reactive mixture from the ejection port, to cool the reactive mixture to form a cooled mixture, and to supply the cooled mixture to the cooled mixture outlet; and a conditioning fluid injection ring disposed at the ejection port and configured to flow a conditioning fluid directly into the reactive mixture as the reactive mixture flows through the ejection port, thereby disturbing the flow of the reactive mixture, creating turbulence within the quench region and cooling the reactive mixture to form a cooled mixture comprising condensed nanoparticles.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to co-pending U.S. patentapplication Ser. No. 11/110,341, filed on Apr. 19, 2005, entitled, “HIGHTHROUGHPUT DISCOVERY OF MATERIALS THROUGH VAPOR PHASE SYNTHESIS” and toco-pending U.S. Provisional Application Ser. No. 60/928,946, filed May11, 2007, entitled “MATERIAL PRODUCTION SYSTEM AND METHOD,” both ofwhich are hereby incorporated by reference as if set forth herein.

FIELD OF THE INVENTION

The present invention relates to methods of and apparatus for quenchinga reactive medium containing gas or vapor phase in order to produceuniform and ultrasmall nanoparticles.

BACKGROUND OF THE INVENTION

Gas or vapor phase particle production is an important technique forproducing engineered nanoparticles. In a particle-producing reactor,basic product species are formed within extremely short time spansfollowing ejection of a hot, reactive medium from an energy deliveryzone. Following ejection from the delivery zone, further formationmechanisms determine the ultimate characteristics of the final product.

Although chemical reactions such as nucleation and surface growth withinprecursor materials occur largely during energy delivery, theseformation mechanisms continue to be active in the first short momentsfollowing ejection. More prevalent in the post-ejection time period arebulk formation mechanisms such as coagulation and coalescence, whichoperate on already formed particles. Any proper conditioning of the hot,reactive medium following ejection from the energy delivery zone mustaccount for these and other formation mechanisms to form a final producthaving desired characteristics. In some instances, maintaining a mixtureat too high a temperature can lead to overly agglomerated particles inthe final product.

In addition to particle formation, proper conditioning must account forpost-formation processing of the product. Although particles, onceformed, cool rapidly through radiative heat loss, the residual gas inwhich they are entrained after formation cools much more slowly, andespecially so when confined. Confinement is necessary to some degree inany controlled-environment processing system, and economic concernsusually dictate relatively small, confining controlled environments.Therefore, such systems must provide efficient mechanisms for cooling ofthe entire gas-particle product, yet also provide for efficienttransport of the product to collection points within the system.

Transport of particles within a gas stream relies on the entrainment ofthe particles, which is largely a function of particle properties, e.g.,mass, temperature, density, and interparticle reactivity, as well as gasproperties, e.g., density, velocity, temperature, density, viscosity,and composite properties, such as particle-gas reactivity. Cooling of agas by definition affects gas temperature, but also may easily lead tochanges in other properties listed above, exclusive of mass.

What is needed in the art is a method of and an apparatus for balancingefficient cooling and transport of a gas-particle product, whichrequires careful optimization of process parameters.

SUMMARY OF THE INVENTION

In the embodiments of the present invention, features and methods areincluded to ensure extremely rapid quenching of reactive mixtures fromvapor phase to solid phase, thereby producing uniform nanoparticles.

In one aspect of the present invention, a particle production system isprovided. The system comprises a plasma production chamber configured toproduce a plasma stream. A reaction chamber is fluidly coupled to theplasma production chamber and has an ejection port. The reaction chamberis configured to receive the plasma stream from the plasma productionchamber, vaporize a precursor material with the plasma stream to form areactive mixture stream comprising the vaporized precursor materialentrained within plasma stream, and supply the reactive mixture streamto the ejection port. The system also comprises a quench chamber havinga wide end, a narrow end, a frusto-conical surface that narrows as itextends from the wide end to the narrow end away from the ejection portof the reaction chamber, a cooled mixture outlet formed at the narrowend, and a quench region formed within the quench chamber between theejection port and the cooled mixture outlet. The quench region isfluidly coupled to the ejection port of the reaction chamber and isconfigured to receive the reactive mixture stream from the ejection portof the reaction chamber, to cool the reactive mixture stream to form acooled mixture stream, and to supply the cooled mixture stream to thecooled mixture outlet. A conditioning fluid injection ring is disposedat the ejection port of the reaction chamber and configured to flow aconditioning fluid directly into the reactive mixture stream as thereactive mixture stream flows through the ejection port of the reactionchamber, thereby disturbing the flow of the reactive mixture stream,creating turbulence within the quench region and cooling the reactivemixture stream to form a cooled mixture stream comprising condensednanoparticles.

In another aspect of the present invention, a method of producinguniform particles is provided. The method comprises producing a plasmastream within a plasma production chamber, applying the plasma stream toa precursor material, and vaporizing the precursor material with theplasma stream within a reaction chamber, thereby forming a reactivemixture stream comprising the vaporized precursor material entrainedwithin the plasma stream. The reaction chamber is fluidly coupled to theplasma production chamber and has an ejection port. The reactive mixturestream flows through the ejection port and into a quench region of aquench chamber. The quench chamber has a wide end, a narrow end, afrusto-conical surface that narrows as it extends from the wide end tothe narrow end away from the ejection port of the reaction chamber, acooled mixture outlet formed at the narrow end, and the quench regionformed within the quench chamber between the ejection port and thecooled mixture outlet. A conditioning fluid flows through an injectionring disposed at the ejection port of the reaction chamber. Theconditioning fluid flows directly into the reactive mixture stream asthe reactive mixture stream flows through the ejection port of thereaction chamber, thereby disturbing the flow of the reactive mixturestream and creating turbulence within the quench region. The reactivemixture stream is quenched within the quench region to form a cooledmixture stream comprising condensed nanoparticles. The cooled mixturestream flows through the cooled mixture outlet of the quench chamber.

In preferred embodiments, the quench chamber further comprises anannular supply portion disposed between the perimeter of the reactionchamber and the frusto-conical surface. The annular supply portionsupplies a conditioning fluid into the quench region in an annularformation along a path different from the flow of the conditioning fluidthrough the conditioning fluid injection ring. In some embodiments, theannular supply portion comprises a plurality of supply ports disposed inan annular formation around the reaction chamber. In other embodiments,the annular supply portion comprises one continuous supply port disposedin an annular formation around the reaction chamber.

In preferred embodiments, the conditioning fluid injection ring flowsthe conditioning fluid directly into the reactive mixture stream at anangle substantially perpendicular to the flow of the reactive mixturestream.

In some embodiments the conditioning fluid is a gas. In someembodiments, the conditioning fluid is super-cooled gas or liquid gas,including, but not limited to, liquid nitrogen and liquid helium. Thetype and form of the conditioning fluid flowing through the injectionring can be the same or different from the conditioning fluid flowingthrough the annular supply portion.

It is contemplated that the plasma stream can be produced in a varietyof ways. However, in a preferred embodiment, the plasma productionchamber produces the plasma stream by energizing a working gas.

In some embodiments, the precursor material flows directly into theplasma production chamber via a precursor supply port on the plasmaproduction chamber prior to its vaporization. Additionally oralternatively, the precursor material can flow directly into thereaction chamber via a precursor supply port on the reaction chamberprior to its vaporization.

In preferred embodiments, the reaction chamber comprises an insulatingmaterial, thereby forming a enthalpy maintenance region within thereaction chamber. In this respect, the enthalpy of the reactive mixturestream can be maintained at a predetermined threshold level for a periodof time within the enthalpy maintenance region of the reaction chamber.Preferably, the reaction chamber comprises a ceramic material.

In preferred embodiments, a collection device is fluidly coupled to thecooled mixture outlet of the quench chamber via a conduit. The conduitpreferably has substantially the same diameter as the cooled mixtureoutlet. The collection device receives the cooled mixture stream fromthe quench region and separates condensed particles from the cooledmixture stream. Ideally, these condensed particles are nanoparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of a system forproducing uniform nanoparticles using a quench chamber in accordancewith the principles of the present invention.

FIG. 2 is a graph illustrating average mixture temperature in relationto time and distance as material is introduced, vaporized and cooledwithin embodiments of the present invention.

FIG. 3 is a schematic illustration of one embodiment of a system forproducing uniform nanoparticles using a quench gas in a turbulent quenchchamber in accordance with principles of the present invention.

FIG. 4 is a schematic illustration of one embodiment of a system forproducing uniform nanoparticles using a liquid conditioning fluid in aturbulent quench chamber in accordance with the principles of thepresent invention.

FIG. 5 is a flowchart illustrating one embodiment of a method ofproducing uniform nanoparticles in accordance with the principles of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The description below concerns several embodiments of the invention. Thediscussion references the illustrated preferred embodiment. However, thescope of the present invention is not limited to either the illustratedembodiment, nor is it limited to those discussed. To the contrary, thescope should be interpreted as broadly as possible based on the languageof the Claims section of this document.

In the following description, numerous details and alternatives are setforth for purpose of explanation. However, one of ordinary skill in theart will realize that the invention can be practiced without the use ofthese specific details. In other instances, well-known structures anddevices are shown in block diagram form in order not to obscure thedescription of the invention with unnecessary detail.

This disclosure refers to both particles and powders. These two termsare equivalent, except for the caveat that a singular “powder” refers toa collection of particles. The present invention may apply to a widevariety of powders and particles. Powders that fall within the scope ofthe present invention may include, but are not limited to, any of thefollowing: (a) nano-structured powders(nano-powders), having an averagegrain size less than 250 nanometers and an aspect ratio between one andone million; (b) submicron powders, having an average grain size lessthan 1 micron and an aspect ratio between one and one million; (c)ultra-fine powders, having an average grain size less than 100 micronsand an aspect ratio between one and one million; and (d) fine powders,having an average grain size less than 500 microns and an aspect ratiobetween one and one million.

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings. Tofacilitate this description, like reference numerals designate likeelements.

Preferably, the dimensions of the quench chamber of the presentinvention have the following general relationships: the diameter of thewide end is substantially greater than that of the ejection port of thereaction chamber, the diameters of the one or more conditioning fluidsupply ports are substantially smaller than that of the injection port,the diameter of the narrow end of the constricting chamber issubstantially smaller than the diameter of the wide end andsubstantially equal to the diameter of the ejection port. Additionally,because of the inclusion of the annulus of smaller ports, the diameterof the ejection port is necessarily smaller than that of the wide end ofthe quench chamber. More specifically, the constricting chamberpreferably has a first dimension of approximately 12 inches,constricting to a second dimension of approximately two inches over adistance of 24 inches. Preferred aspect ratios, i.e., ratios of thefirst diameter to the distance between the first and second ends, rangebetween one to three and one to two.

Flow of the conditioning fluid into the one or more supply ports ispreferably caused by formation of a negative pressure differential withthe cooled mixture outlet, which also aids in maintaining flow of themixture through the chamber. This negative pressure differential ispreferably formed by fluidly coupling a suction generator or vacuumformation system with the cooled mixture outlet. In alternativeembodiments, active injection of conditioning fluid is contemplated, butthis scheme has many disadvantages when compared to passively drawingconditioning fluid into the system by vacuum.

Because the present invention preferably uses a pressure differential tomotivate flow of the conditioning fluid through the one or more supplyports, variation of the combined surface area of the one or more supplyports allows variation of the flow rate of conditioning fluid. Asdescribed below, in some configurations a difference in flow ratesbetween the conditioning fluid sheath and the reactive gas vaporcontributes to a conditioning effect of the fluid. Therefore, adjustmentof the flow rate of the conditioning fluid permits optimization of theconditioning effect that a flow rate differential provides.

Within the present invention, many configurations of the smoothlyvarying constrictions of the chamber are contemplated. In the preferredembodiments, these constrictions will smoothly vary in such a way so asto accelerate fluid flow and provide a Venturi-effect pressuredifferential within the quench chamber. In general, the constrictionshape is determined while accounting for several factors affecting theconditioning of the reactive gas-vapor. Two factors are of majorconcern. First, adequate space must be provided within the regionproximal to the first end of the constricting chamber to accommodaterapid expansion of the hot gas-vapor following its flowing into thechamber. Second, constriction of the chamber within the region proximalto the narrow end of the constricting chamber must not occur so rapidlythat undue turbulence is introduced into the gas-vapor as it flows tothe cooled mixture outlet. For any chamber having fixed length betweenthe wide and narrow ends, these requirements present contradictorydesign concerns. However, the several embodiments of the presentinvention include designs that accommodate both concerns.

In a preferred configuration for constrictions within the quenchchamber, a cone like (frusto-conical) surface constricts, at a constantrate or otherwise, from the wide end to the cooled mixture outlet at thenarrow end. The quench chamber of the present invention preferablycomprises a thin shell. The exterior of the quench chamber is can becooled by a fluid cooling system, to dissipate heat absorbed into thebody of the quench chamber from the gas particle mixture. As mentionedabove, this heat will primarily be supplied to the quench chamber bodyin the form of radiation from the newly formed particles as the rapidlycool within the quench chamber. In order to avoid overheating of thechamber body, the fluid cooling system is preferably included.

The present invention considers a wide variety of gas phase particleproduction systems including combustion-based systems, plasma basedsystems, laser ablation systems and vapor deposition systems. Thepreferred systems take material inputs in a broad range of forms,including solid phase inputs, and provide product in high surface areaforms, including nanopowders. In addition, the process controlspreferably provide a fine degree over a plurality of reactionparameters, permitting fine gradients of product composition ratios tobe produced.

A wide variety of material types and forms can be processed inpreferable particle production reactors used in the present invention.Without prejudice, the present invention specifically considers theprovision of materials in the following forms: solid, liquid and gas. Anexemplary particle production system is a plasma powder productionreactor, which is included within several of the exemplary embodimentsdiscussed below. The plasma reactors considered within the presentinvention can have many means of energy delivery, including thefollowing: DC coupling, capacitive coupling, inductive coupling, andresonant coupling. In general, vapor phase nanopowder production meansare preferred. The embodiments of the present invention can use elementsof nano-powder production systems similar to those disclosed in U.S.patent application Ser. No. 11/110,341, filed on Apr. 19, 2005 andentitled, “HIGH THROUGHPUT DISCOVERY OF MATERIALS THROUGH VAPOR PHASESYNTHESIS”, which is currently published as U.S. Publication No.2005-0233380-A. In such a nano-powder production system, working gas issupplied from a gas source to a plasma reactor. Within the plasmareactor, energy is delivered to the working gas, thereby creating aplasma. A variety of different means can be employed to deliver thisenergy, including, but not limited to, DC coupling, capacitive coupling,inductive coupling, and resonant coupling. One or more materialdispensing devices introduce at least one material, preferably in powderform, into the plasma reactor. The combination within the plasma reactorof the plasma and the material(s) introduced by the material dispensingdevice(s) forms a highly reactive and energetic mixture, wherein thepowder can be vaporized. This mixture of vaporized powder moves throughthe plasma reactor in the flow direction of the working gas.

Referring now to FIG. 1, the particle production system 100 comprises aplasma production unit 120 having plasma production chamber 125. Theplasma production chamber 125 is preferably disposed within the plasmaproduction unit 120, which can include several types of inputs forpower, gas, and precursor materials. Inputs are provided to the plasmaproduction chamber 125 by a variety of supply systems.

The plasma production unit 120 is configured to produce a plasma streamwithin the plasma production chamber 125. It is contemplated that theplasma stream can be produced in a variety of ways. However, in apreferred embodiment, a working gas flows from a working gas supplydevice 110 into the plasma production chamber 125, where energy isdelivered to it, thereby forming the plasma stream. Preferably, anoverall system controller provides control signals to the working gassupply device 110. Additionally, a power supply system (not shown) canalso be coupled to the plasma production chamber 125. Preferably, theoverall system controller provides control signals to the power supplysystem as well.

A reaction chamber 140 is fluidly coupled to the plasma productionchamber 125 and configured to receive the plasma stream from the plasmaproduction chamber 125. In a preferred embodiment, the reaction chamber140 has a larger diameter than the plasma production chamber 125.

In some embodiments, the plasma production chamber 125 is fluidlycoupled with a material supply device 130, thereby allowing precursormaterial, such as powder, from the material supply device 130 to bedelivered directly into the plasma production chamber 125. Precursormaterial is stored within the material supply 130. A material supplyconduit preferably passes from the material supply device 130 to theplasma production chamber 125. The material supply device 130 preferablyincludes a controllable delivery system that provides material to theconduit. Preferably, the conduit enters though airtight seals andterminates within the plasma production unit 120 at a selected location.Furthermore, an overall system controller is preferably configured tosupply control signals to the material supply device 130. Additionallyor alternatively, the material supply device 130 can be fluidly coupleddirectly to the reaction chamber 140, thereby allowing precursormaterial from the material supply device 130 to be delivered directlyinto the reaction chamber 140.

In embodiments where the precursor material is delivered into the plasmaproduction chamber 125, the plasma stream mixes with the precursormaterial, forming a reactive mixture stream. The coupling between theplasma production chamber 125 and the reaction chamber 140 permitsdelivery of the mixture stream from the plasma production unit 120 intothe reaction chamber 140.

In some embodiments, portions of the reaction chamber 140 areconstructed of an insulating material configured to maintain theenthalpy of a plasma stream within a portion thereof above apredetermined threshold. Preferably, maintaining the enthalpy of theplasma extends a resonance time of the plasma within the reactionchamber 140. In some embodiments, portions of the reaction chamber 140are constructed of a material with high thermal durability. In theseembodiments, the portions so constructed are configured to attain a hightemperature during operation of the reaction chamber 140. In someembodiments, portions of the reaction chamber 140 are constructed of aceramic material. Preferably, the material used is boron nitride.

Within the reaction chamber 140, the plasma stream preferably vaporizesthe precursor material, thereby forming a reactive mixture streamcomprising the vaporized precursor material entrained within the plasmastream. In some embodiments, this vaporization of precursor material canbegin in the plasma production chamber 125 if the precursor material isintroduced into the plasma production chamber 125.

Preferably, reaction chamber 140 is shaped and the operationalparameters of the system 100 are controlled so that as the mixturestream enters the reaction chamber 140, it is maintained above anenthalpy threshold. This maintenance takes place within an enthalpymaintenance region somewhere within the reaction chamber 140.Preferably, the average enthalpy of the mixture stream falls as it movesaway from the enthalpy maintenance region with its minimum enthalpy(within the reaction chamber 140) coming at the ejection port to thequench region 155. In some embodiments, the resonance time of themixture within the chamber 140 is above a threshold length of timecontrolled by an overall system controller.

Furthermore, in some embodiments of the present invention, the reactionchamber 140 is constructed and the operational parameters of theapparatus 100 are chosen so that the vaporized precursor material beginsto condense within the mixture stream while it is within the reactionchamber 140. In some other embodiments, construction and operationalparameters of the system 100 are chosen so that the vaporized precursormaterial begins to condense within the mixture stream while it is withinthe quench region 155.

A quench chamber 150 is fluidly coupled to the reaction chamber 140through an ejection port at the end of the reaction chamber 140. Theejection port is configured to supply the reactive mixture stream fromthe reaction chamber 140 into a quench region 155 of the quench chamber150. In a preferred embodiment, the reaction chamber 150 has afrusto-conical shape, narrowing as it extends away from the ejectionport and towards a cooled mixture outlet. Although the figures showquench chamber 150 substantially open at the wide end, preferably thewide end of the quench chamber 150 is substantially closed except forfluid ports through which a fluid can be received. The cooled mixtureoutlet is disposed at the narrow end of the quench chamber 150 thatpreferably leads into a cooling conduit 160. The quench region 155 isformed within the quench chamber 150 between the ejection port of thereaction chamber 140 and the cooled mixture outlet. In a preferredembodiment, an annular supply portion is formed between the perimeter ofthe reaction chamber 140 and the quench chamber 150. This annular supplyportion can comprise a plurality of supply inlets or one continuoussupply inlet disposed in an annular formation around the ejection portof the reaction chamber 140. The annular supply portion is configured tosupply a conditioning fluid, preferably from a conditioning fluid supplydevice, to the quench region 155. In a preferred embodiment, thesesupply inlets are channels of adjustable size that directly couple theconditioning fluid supply to the quench region 155, yet permit forcontrolled flow of the conditioning fluid to the quench region 155. InFIG. 1, conditioning gas is supplied roughly along the vectors marked“Quench Gas.” In a preferred embodiment, the conditioning fluid issupplied through airtight inlets and outlets to the quench region 155(preferably from a dedicated supply of conditioning fluid), where itpreferably mixes with and cools the reactive mixture stream from thereaction chamber 140.

Motive fluid flow within the system can be motivated by a suctiongenerator 180, such as a motive vacuum pump, pulling a negative pressureon a cooling conduit 160 that is fluidly coupled to the cooled mixtureoutlet of the quench chamber 150, thereby motivating mass flow throughthe outlet of the quench region 155. However, the flow rate of themotive fluid into the quench region 155 is preferably controlled by theoverall control system.

The cooling conduit 160 receives the particle and gas mixture from thequench region 155. Preferably, the mixture is pulled into the coolingconduit 160 by the suction generator 180. However, in some embodiments,a motive pump or other system within a sampling or collection device 170provides some motive force to pull the mixture. Of course, to someextent, pressure provided by the plasma production chamber 125 and theconditioning fluid supply can motivate the flow of the mixture into thecooling conduit 160. In some embodiments, the cooling conduit 160 isequipped with an active cooling system.

In some embodiments, a conditioning fluid, such as argon, is suppliedinto the gas input couplings of the cooling conduit 160. In some ofthese embodiments, the conditioning fluid is a cooling and entraininggas. In some of these embodiments, the conditioning fluid is apassivating gas.

The cooling conduit 160 fluidly connects the quench region 155 with asampling or collection device 170. The conduit 160 is preferably coupledto the quench region 155 through airtight means. The collection device170 is preferably positioned between the cooling conduit 160 and thesuction generator 180. The collection device 170 is configured toreceive the cooled mixture via the cooling conduit 160, sample orcollect material, such as condensed particles, having appropriatecharacteristics from the mixture, and permit remains of the mixture toflow to the suction generator 180, which is fluidly coupled through aconduit. Furthermore, the collection device 170 can take multiplesamples, at selected times, and can sample discontinuously, which allowsfor sampling from a gas-particle streams whose composition may vary fromtime to time without contamination from previous product.

It is contemplated that the collection device 170 can be configured in avariety of ways. In one embodiment, the collection device 170 comprisesa sampling structure, at least one filled aperture formed in thesampling structure, and at least one unfilled aperture formed in thesampling structure. Each filled aperture is configured to collectparticles from the mixture stream, such as by using a filter. Thesampling structure is configured to be adjusted between a pass-throughconfiguration and a collection configuration. The pass-throughconfiguration comprises an unfilled aperture being fluidly aligned witha conduit, such as the cooling conduit 280, thereby allowing theunfilled aperture to receive the mixture stream from the conduit and themixture stream to flow through the sampling structure withoutsubstantially altering the particle content of the mixture stream. Thecollection configuration comprises a filled aperture being fluidlyaligned with the conduit, thereby allowing the filled aperture toreceive the mixture stream and collect particles while the mixturestream is being flown through the filled aperture.

It is contemplated that the sampling structure can be adjusted betweenthe pass-through configuration and the collection configuration in avariety of ways. In one embodiment, the sampling structure is adisk-shaped structure including an annular array of apertures, whereinthe annular array comprises a plurality of the filled apertures and aplurality of the unfilled apertures. The sampling structure is rotatablymounted to a base, wherein rotational movement of the sampling structureresults in the adjustment of the sampling structure between thepass-through configuration and the collection configuration. In anotherembodiment, the sampling structure is a rectangular-shaped structureincluding a linear array of apertures, wherein the linear arraycomprises a plurality of the filled apertures and a plurality of theunfilled apertures. The sampling structure is slideably mounted to abase, wherein sliding of the sampling structure results in theadjustment of the sampling structure between the pass-throughconfiguration and the collection configuration.

As mentioned above, the collection device 170 preferably permits thesuction generator 180 to provide a motive force therethrough. However,in some embodiments, the collection device 170 provides additionalmotive force. In some embodiments, a collection device 170 supplants themotive force provided by the suction generator 180 and provides asubstitute motive force to the cooling conduit 160.

The overall control system (not shown) sends signals to the working gassupply 110 and power supply to set operational parameters. Parametersfor the working gas supply 110 determine the rate at which the workinggas feeds into the plasma production chamber 125. Power supplyparameters determine the voltage and amperage at which power is suppliedto the plasma production chamber 125. In combination, these parametersdetermine the characteristics of the plasma produced within the plasmaproduction chamber 125. Furthermore, the material supply device 130provides a metered stream of material through the material supplyconduit to the conduit's terminus location within the plasma productionchamber 125. This exposes the material to plasma within the chamber. Therate at which material is provided into the chamber 125 preferably isdetermined by the overall control system. This rate, and other systemparameters, determines characteristics of the mixture stream formedwithin the plasma production chamber 125. Furthermore, although thematerial supply device 130 is described as providing only a singlematerial into the plasma production chamber 125 at a single location, insome embodiments of the present invention, the material supply device130 supplies a plurality of materials into the plasma production chamber125 and/or the reaction chamber 140 at one or more locations.

In the system 100, the mass flow rate of material through the system iscontrolled to permit effective quenching at achievable conditioningfluid flow rates. Preferably, this rate is controlled via the mass flowrate of material into the plasma production chamber 125. Specifically,the material supply device 130 and the control system are configured tocontrol a mass flow rate delivery of the precursor material into theplasma stream to achieve a rate that permits cooling of the mixturestream to one quarter of the melting point of the material extremelyrapidly. Preferably, this flow rate is selected with reference toachievable conditioning fluid flow rates within the quench region 155and with reference to achievable turbulence within the quench region155.

While the configuration of system 100 provides an improvement in termsof quench rate over the prior art, the quench rate can be furtherimproved. FIGS. 3 and 4 illustrate systems similar to system 100, butwith additional features that result in an improved quench rate.

FIG. 3 illustrates one embodiment of a particle production system 300.In the system 300, the reactive mixture flows from the reactor chamber140 into the quench region 155, such as in FIG. 1. While the mixtureflows into the quench region 155, conditioning fluid, labeled “QuenchGas” is supplied into the quench region 155 via an annular supplyportion similar to the annular supply portion discussed above. A portionof the conditioning fluid is diverted or other wise supplied to aninjection ring disposed at the end of the reaction chamber 140. Thisinjection ring is configured to flow the quench gas directly into thereactive mixture stream as the reactive mixture stream flows through theejection port of the reaction chamber 140, thereby disturbing the flowof the reactive mixture stream, creating turbulence within the quenchregion and cooling the reactive mixture stream at the earliest pointpossible as the mixture leaves the reaction chamber.

It is contemplated that the injection ring can be configured in avariety of ways. In preferred embodiments, the injection ring flows theconditioning fluid directly into the reactive mixture stream at an anglesubstantially perpendicular to the flow of the reactive mixture stream.However, it is contemplated that other injection angles are within thescope of the present invention as well. Furthermore, in a preferredembodiment, the injection ring comprises a plurality of injection ports,such as nozzle structures 352 and 354, disposed in an annularconfiguration around flow of the reactive mixture. The injection ring isconfigured to induce a high degree of turbulence within the conditioningfluid and the reactive mixture, and ultimately the quench region 155.

As the reactive mixture moves out of the reaction chamber 140, itexpands and mixes with the conditioning fluid. Parameters related toconditioning fluid supply are controlled to permit the nozzles 352 and354 to produce a high degree of turbulence and promote mixing with thereactive mixture. This turbulence can depend on many parameters.Preferably, one or more of these parameters are adjustable to controlthe level of turbulence. These factors include, but are not limited to,the flow rates of the conditioning fluid and any modification to theflow path of the fluid.

After entering the quench region 155, particle formation mechanisms areactive. The degree to which the particles agglomerate depends on therate of cooling. The cooling rate depends on the turbulence of the flowwithin the quench region. Preferably, the system is adjusted to form ahighly turbulent flow, and to form very dispersed particles. Forexample, in preferred embodiments, the turbidity of the flow within thequench region is such that the flow has a Reynolds Number of at least1000. Preferably, the turbulence is controlled to achieve a rate ofcooling of the mixture stream that moves the mixture stream temperatureto one quarter of the melting point of the material within a very shorttime after the reactive mixture exits the reaction chamber 140.

Following injection into the quench region, cooling, and particleformation, the mixture flows from the quench chamber 150 into thecooling conduit 160. Suction generated by an external device, such asthe suction generator previously discussed, preferably moves the cooledmixture from the quench region 155 into the conduit 160. The cooledmixture can flow to a collection or sampling device, such as describedabove with respect to FIG. 1.

In FIG. 3, the conditioning fluid supplied to the quench region throughthe injection ring disposed at the ejection port of the reaction chamber140 and through the annular supply portion disposed between theperimeter of the reaction chamber 140 and the quench chamber 150 is agas. In one embodiment, the gas supplied is argon. However, other gasescan be used as well.

It is contemplated that in addition to a gas being used as theconditioning fluid, a super-cooled gas, or liquid gas, can be used asthe conditioning fluid. Such conditioning fluids include, but are notlimited to, liquid nitrogen and liquid helium. In FIG. 4, system 400provides a conditioning fluid to the quench region 155 in the form of aliquid gas, which is labeled as “Quench Liquid.” In a preferredembodiment, the quench liquid flows through an injection ring directlyinto the reactive mixture as the reactive mixture leaves the reactionchamber 140, similar to the quench gas described above with respect toFIG. 3. However, it is contemplated that any combination orconfiguration of the features illustrated in FIGS. 2-4 are within thescope of the present invention. For example, a quench gas can besupplied through the annular supply portion, while a quench liquid issupplied through the injection ring. Alternatively, the quench liquidcan be supplied through the annular supply portion and into the quenchregion 155 without the use of the injection ring.

Preferably the temperature of the liquid and the flow rate thereof areconfigured to achieve a rate of cooling of the mixture stream that movesthe mixture stream temperature to one quarter of the melting point ofthe material within an extremely short time after the reactive mixtureleaves the reaction chamber 140. The hot reactive mixture absorbs themoisture from the quench liquid, thus resulting in an increased quenchrate above that achieved by only using a quench gas. Preferably thetemperature and conditioning liquid flow rate are selected withreference to desired mass flow rates within the system.

FIG. 5 is a flowchart illustrating one embodiment of a method 500 ofproducing uniform nanoparticles in accordance with the principles of thepresent invention. As would be appreciated by those of ordinary skill inthe art, the protocols, processes, and procedures described herein maybe repeated continuously or as often as necessary to satisfy the needsdescribed herein. Additionally, although the steps of method 500 areshown in a specific order, certain steps may occur simultaneously or ina different order than is illustrated. Accordingly, the method steps ofthe present invention should not be limited to any particular orderunless either explicitly or implicitly stated in the claims.

At step 510, a plasma stream is produced within a plasma productionchamber. It is contemplated that the plasma stream can be produced in avariety of ways. However, in a preferred embodiment, the plasmaproduction chamber produces the plasma stream by energizing a workinggas that flows through the chamber.

At step 520, the plasma stream is applied to a precursor material,thereby vaporizing the precursor material. This application of theplasma stream to the precursor material can tale place in the plasmaproduction chamber and/or in a reaction chamber fluidly coupled to theplasma production chamber. Either way, the plasma stream flows into thereaction chamber and a reactive mixture stream is formed within thereaction chamber. The reactive mixture stream preferably comprises thevaporized material entrained within the plasma stream.

At step 530, the reactive mixture stream flows through the ejection portof the reaction chamber and into a quench region of a quench chamber.The quench chamber has a wide end, a narrow end, a frusto-conicalsurface that narrows as it extends from the wide end to the narrow endaway from the ejection port of the reaction chamber, a cooled mixtureoutlet formed at the narrow end, and the quench region formed within thequench chamber between the ejection port and the cooled mixture outlet.

At step 540, a conditioning fluid flows through an injection ringdisposed at the ejection port of the reaction chamber. The conditioningfluid flows directly into the reactive mixture stream as the reactivemixture stream flows through the ejection port of the reaction chamber,thereby disturbing the flow of the reactive mixture stream and creatingturbulence within the quench region. As discussed above, theconditioning fluid is preferably a gas or a liquid gas. Additionally, oralternatively, the conditioning fluid can be supplied through theannular supply portion disposed between the perimeter of the reactionchamber and the quench chamber.

At step 550, the reactive mixture stream is rapidly quenched within thequench region to form a cooled mixture stream. The cooled mixture streampreferably comprises condensed nanoparticles.

At step 560, the cooled mixture stream flows through the cooled mixtureoutlet of the quench chamber to a collection device., preferably via aconduit. In a preferred embodiment, the conduit has substantially thesame diameter as the cooled mixture outlet.

At step 570, the collection device separates condensed particles fromthe cooled mixture stream as the cooled mixture stream flows through thecollection device. In a preferred embodiment, the collection deviceseparates the condensed particles from the cooled mixture stream byusing one or more filters.

FIG. 2 illustrates a graph 200 showing the intended effect of featuresof embodiments of the present invention on quench rates in particleproduction systems. The graph 200 charts exemplary variations ingas/material or mixture temperature with time (position in theapparatus) as they enter a plasma production chamber, such as chamber125, vaporize or become plasma, mix, travel into a reaction chamber,such as reaction chamber 140, begin to form particles, and enter thequench region, such as quench region 155. Relationships between positionwithin the apparatus and position on the graph are roughly illustratedby vertical correlation between FIGS. 1 and 2.

The vertical axis of the graph charts mixture temperature. The ovallegends denote phases of matter for the material being operated on bythe apparatus. Vapor is on top, below that liquid, and below that solid.The dashed lines indicate critical temperatures relative to the materialconcerned. The ‘bp’ line denotes boiling point, the ‘mp’ line denotedmelting point. The ‘mp/4’ line denotes one quarter of the materialmelting point.

Within the plasma production chamber 125, the temperature rapidlyincreases, causing sublimation of the material from solid phase to vaporphase. As the mixture moves into the reactor chamber, 140 thetemperature and enthalpy of the mixture remain substantially constant,staying within the vapor phase of the material. However, as the mixturemoves to the end of the reaction chamber 140, the temperature decreases,reaching a minimum (within the reaction chamber) at the downstream edgeof the reaction chamber 140.

Once ejected, the mixture enters the quench region 155, where it expandsand cools rapidly. One or more of highly turbulent flow, sufficientlylow mass flow rate, and liquid quenching with super cooled gas formssufficient mixing of the mixture with conditioning fluid to cool themixture smoothly and rapidly through ‘bop’, liquid phase, ‘nip’ and partof solid phase to ‘mp/4’ within a short enough time to avoid undesiredagglomeration and promote the production of uniform nanoparticles. Thesupply of conditioning fluid through the annular supply portion resultsin the quench rate illustrated as line 210. While this quench rate is asubstantial improvement over the prior art, the use of the injectionring and/or the liquid gas results in an even faster quench rateillustrated as line 210′.

During resonance within the reaction chamber and quench region,particles form. Because the mixture is cooled rapidly, there is a shorttime period during which agglomeration occurs. As the mixture ofparticles and hot gas continues to mix with the conditioning fluid, themixture of gas and particles moves out of the narrow end into theconduit. Overall, the quench period within a highly turbulent quenchregion and/or a quench region fed by a super-cooled gas conditioningliquid as in some embodiments of the present invention is much shorterthan with standard quenching. Eventually the conditioning fluid and themixture reach thermal equilibrium, preferably at room temperature.

Thus, features of the embodiments of the present invention decrease theperiod during which particles formed can agglomerate with one another.Ultimately, this decrease in potential agglomeration produces particlesof more uniform size, and in some instances produces smaller-sizedparticles. Both of these features lead to particles with increaseddispersiblity and increased ratio of surface area to volume.

The present invention has been described in terms of specificembodiments incorporating details to facilitate the understanding of theprinciples of construction and operation of the invention. As such,references herein to specific embodiments and details thereof are notintended to limit the scope of the claims appended hereto. It will beapparent to those skilled in the art that modifications can be made tothe embodiments chosen for illustration without departing from thespirit and scope of the invention.

1. A particle production system comprising: a plasma production chamberconfigured to produce a plasma stream; a reaction chamber fluidlycoupled to the plasma production chamber and having an ejection port,wherein the reaction chamber is configured to receive the plasma streamfrom the plasma production chamber, vaporize a precursor material withthe plasma stream to form a reactive mixture stream comprising thevaporized precursor material entrained within plasma stream, and supplythe reactive mixture stream to the ejection port; a quench chamberhaving a wide end, a narrow end, a frusto-conical surface that narrowsas it extends from the wide end to the narrow end away from the ejectionport of the reaction chamber, a cooled mixture outlet formed at thenarrow end, and a quench region formed within the quench chamber betweenthe ejection port and the cooled mixture outlet, wherein the quenchregion is fluidly coupled to the ejection port of the reaction chamberand is configured to receive the reactive mixture stream from theejection port of the reaction chamber, to cool the reactive mixturestream to form a cooled mixture stream, and to supply the cooled mixturestream to the cooled mixture outlet; and a conditioning fluid injectionring disposed at the ejection port of the reaction chamber andconfigured to flow a conditioning fluid directly into the reactivemixture stream as the reactive mixture stream flows through the ejectionport of the reaction chamber, thereby disturbing the flow of thereactive mixture stream, creating turbulence within the quench regionand cooling the reactive mixture stream to form a cooled mixture streamcomprising condensed nanoparticles.
 2. The system of claim 1, furthercomprising an annular supply portion disposed between the perimeter ofthe reaction chamber and the frusto-conical surface, the annular supplyportion fluidly coupled to the quench region and configured to supply aconditioning fluid into the quench region in an annular formation alonga path different from the flow of the conditioning fluid through theconditioning fluid injection ring.
 3. The system of claim 2, wherein theannular supply portion comprises a plurality of supply ports disposed inan annular formation around the reaction chamber.
 4. The system of claim2, wherein the annular supply portion comprises one continuous supplyport disposed in an annular formation around the reaction chamber. 5.The system of claim 1, wherein the conditioning fluid injection ring isconfigured to flow the conditioning fluid directly into the reactivemixture stream at an angle substantially perpendicular to the flow ofthe reactive mixture stream.
 6. The system of claim 1, wherein theplasma production chamber is configured to form the plasma stream byenergizing a working gas.
 7. The system of claim 1, wherein the plasmaproduction chamber comprises a precursor supply port configured tosupply the precursor material directly into the plasma productionchamber prior to its vaporization.
 8. The system of claim 1, wherein thereaction chamber comprises a precursor supply port configured to supplythe precursor material directly into the reaction chamber prior to itsvaporization.
 9. The system of claim 1, wherein the reaction chamber isformed from insulating material.
 10. The system of claim 9, wherein thereaction chamber comprises a ceramic material.
 11. The system of claim1, further comprising a collection device fluidly coupled to the cooledmixture outlet of the quench chamber via a conduit, the conduit havingsubstantially the same diameter as the cooled mixture outlet, whereinthe collection device is configured to receive the cooled mixture streamfrom the quench region and separate condensed particles from the cooledmixture stream.
 12. A method of producing nanoparticles, the methodcomprising: vaporizing a precursor material with a plasma stream withina reaction chamber, thereby forming a reactive mixture stream comprisingthe vaporized precursor material entrained within the plasma stream;flowing the reactive mixture stream through an ejection port of thereaction chamber and into a quench region of a quench chamber afrusto-conical surface that narrows as it extends away from the ejectionport of the reaction chamber; flowing a conditioning fluid through aninjection ring disposed at the ejection port of the reaction chamberinto the reactive mixture stream as the reactive mixture stream flowsthrough the ejection port of the reaction chamber, thereby disturbingthe flow of the reactive mixture stream and creating turbulence withinthe quench region; and quenching the reactive mixture stream within thequench region to form a cooled mixture stream comprising condensednanoparticles; and flowing the cooled mixture stream through a cooledmixture outlet of the quench chamber.
 13. The method of claim 12,further comprising supplying a conditioning fluid into the quench regionin an annular formation along a path different from the flow of theconditioning fluid through the conditioning fluid injection ring via anannular supply portion formed between the reaction chamber and thefrusto-conical surface of the quench chamber.
 14. The method of claim13, wherein the annular supply portion comprises a plurality of supplyports disposed in an annular formation around the reaction chamber. 15.The method of claim 13, wherein the annular supply portion comprises onecontinuous supply port disposed in an annular formation around thereaction chamber.
 16. The method of claim 12, wherein the conditioningfluid injection ring flows the conditioning fluid into the reactivemixture stream at an angle substantially perpendicular to the flow ofthe reactive mixture stream.
 17. The method of claim 12, wherein theconditioning fluid is a super-cooled gas.
 18. The method of claim 12,wherein the conditioning fluid is liquid nitrogen.
 19. The method ofclaim 12, wherein the conditioning fluid is liquid helium.
 20. Themethod of claim 12, wherein the plasma stream is produced within aplasma production chamber by energizing a working gas.
 21. The method ofclaim 20, further comprising flowing the precursor material into theplasma production chamber via a precursor supply port on the plasmaproduction chamber prior to its vaporization.
 22. The method of claim12, further comprising flowing the precursor material into the reactionchamber via a precursor supply port on the reaction chamber prior to itsvaporization.
 23. The method of claim 12, further comprising maintainingthe enthalpy of the reactive mixture stream for a period of time withinan enthalpy maintenance region within the reaction chamber, wherein thereaction chamber comprises an insulating material.
 24. The method ofclaim 23, wherein the reaction chamber comprises a ceramic material. 25.The method of claim 12, further further comprising: flowing the cooledmixture stream from the quench region to a collection device via aconduit having substantially the same diameter as the cooled mixtureoutlet; and separating condensed nanoparticles from the cooled mixturestream using the collection device.
 26. A method of producingnanoparticles comprising: applying a plasma stream to a precursormaterial within a reaction chamber, thereby forming a reactive mixturestream comprising vaporized precursor material entrained within theplasma stream; flowing the reactive mixture stream through an ejectionport of the reaction chamber and into a frusto-conical-shaped quenchchamber; flowing a conditioning fluid into the reactive mixture streamas the reactive mixture stream flows through the ejection port todisturb the flow of the reactive mixture stream and to cool the reactivemixture stream to form a cooled mixture stream comprising condensednanoparticles.
 27. The method of claim 26, wherein the conditioningfluid flows through an injection ring disposed at the ejection port intothe reactive mixture stream at an angle substantially perpendicular tothe flow of the reactive mixture stream out through the ejection port.28. The method of claim 27, wherein the injection ring induces a highdegree of turbulence within the conditioning fluid and the reactivemixture stream.
 29. The method of claim 27, wherein the injection ringcomprises one or more injection ports.
 30. The method of claim 26,wherein the plasma stream is produced within a plasma productionchamber.
 31. The method of claim 30, further comprising supplying theprecursor material into the plasma production chamber prior to itsvaporization.
 32. The method of claim 26, further comprising supplyingthe precursor material into the reaction chamber prior to itsvaporization.